Jiangfeng Qian

High rate and stable cycling of lithium metal anode

Lithium metal is an ideal battery anode. However, dendrite growth and limited Coulombic efficiency during cycling have prevented its practical application in rechargeable batteries. Herein, we report that the use of highly concentrated electrolytes composed of ether solvents and the lithium bis(fluorosulfonyl)imide salt enables the high-rate cycling of a lithium metal anode at high Coulombic efficiency (up to 99.1%) without dendrite growth. With 4 M lithium bis(fluorosulfonyl)imide in 1,2-dimethoxyethane as the electrolyte, a lithium|lithium cell can be cycled at 10 mA cm−2 for more than 6,000 cycles, and a copper|lithium cell can be cycled at 4 mA cm−2 for more than 1,000 cycles with an average Coulombic efficiency of 98.4%. These excellent performances can be attributed to the increased solvent coordination and increased availability of lithium ion concentration in the electrolyte. Further development of this electrolyte may enable practical applications for lithium metal anode in rechargeable batteries.

High Capacity and Rate Capability of Amorphous Phosphorus for Sodium Ion Batteries

Turning on your P/C: An amorphous phosphorus/carbon (a-P/C) composite was synthesized using simple mechanical ball milling of red phosphorus and conductive carbon powders. This material gave an extraordinarily high sodium ion storage capacity of 1764 mA h g(-1) (see graph) with a very high rate capability, showing great promise as a high capacity and high rate anode material for sodium ion batteries.

Sb–C nanofibers with long cycle life as an anode material for high-performance sodium-ion batteries

Sb–C nanofibers are synthesized successfully through a single-nozzle electrospinning technique and subsequent calcination. The structural and morphological characterizations reveal the uniform nanofiber structure with the Sb nanoparticles embedded homogeneously in the carbon nanofibers. Electrochemical experiments show that the Sb–C nanofiber electrode can deliver large reversible capacity (631 mA h g−1) at C/15, greatly improved rate capability (337 mA h g−1 at 5 C) and excellent cycling stability (90% capacity retention after 400 cycles). The superior electrochemical performances of the Sb–C nanofibers are due to the unique nanofiber structure and uniform distribution of Sb nanoparticles in carbon matrix, which provides a conductive and buffering matrix for effective release of mechanical stress caused by Na ion insertion/extraction and prevent the aggregation of the Sb nanoparticles.

Synergistic Na-Storage Reactions in Sn4P3 as a High-Capacity, Cycle-stable Anode of Na-Ion Batteries

Room-temperature Na-ion batteries have attracted great interest as a low cost and environmentally benign technology for large scale electric energy storage, however their development is hindered by the lack of suitable anodic host materials. In this paper, we described a green approach for the synthesis of Sn4P3/C nanocomposite and demonstrated its excellent Na-storage performance as a novel anode of Na-ion batteries. This Sn4P3/C anode can deliver a very high reversible capacity of 850 mA h g(-1) with a remarkable rate capability with 50% capacity output at 500 mA g(-1) and can also be cycled with 86% capacity retention over 150 cycles due to a synergistic Na-storage mechanism in the Sn4P3 anode, where the Sn nanoparticles act as electronic channels to enable electrochemical activation of the P component, while the elemental P and its sodiated product Na3P serve as a host matrix to alleviate the aggregation of the Sn particles during Na insertion reaction. This mechanism may offer a new approach to create high capacity and cycle-stable alloy anodes for Na-ion batteries and other electrochemical energy storage applications.

Mesoporous Amorphous FePO4 Nanospheres as High-Performance Cathode Material for Sodium-Ion Batteries

FePO4 nanospheres are synthesized successfully through a simple chemically induced precipitation method. The nanospheres present a mesoporous amorphous structure. Electrochemical experiments show that the FePO4/C electrode demonstrates a high initial discharging capacity of 151 mAh g(-1) at 20 mA g(-1), stable cyclablilty (94% capacity retention ratio over 160 cycles), as well as high rate capability (44 mAh g(-1) at 1000 mA g(-1)) for Na-ion storage. The superior electrochemical performance of the FePO4/C nanocomposite is due to its particular mesoporous amorphous structure and close contact with the carbon framework, which significantly improve the ionic and electronic transport and intercalation kinetics of Na ions.

Synthesis and electrochemical behaviors of layered Na0.67[Mn0.65Co0.2Ni0.15]O2 microflakes as a stable cathode material for sodium-ion batteries

Stable Na+ ion storage cathodes with adequate reversible capacity are now greatly needed for enabling Na-ion battery technology for large scale and low cost electric storage applications. In light of the superior Li+ ion storage performance of layered oxides, pure P2-phase Na0.67[Mn0.65Ni0.15Co0.2]O2 microflakes are synthesized by a simple sol–gel method and tested as a Na+ ion storage cathode. These layered microflakes exhibit a considerably high reversible capacity of 141 mA h g−1 and a slow capacity decay to 125 mA h g−1 after 50 cycles, showing much better cyclability than previous NaMnO2 compounds. To further enhance the structural and cycling stability, we partially substituted Co3+ by Al3+ ions in the transition-metal layer to synthesize Na0.67[Mn0.65Ni0.15Co0.15Al0.05]O2. As expected, the Al-substituted material demonstrates a greatly improved cycling stability with a 95.4% capacity retention over 50 cycles, possibly serving as a high capacity and stable cathode for Na-ion battery applications.

Dendrite-Free Lithium Deposition with Self-Aligned Nanorod Structure

Suppressing lithium (Li) dendrite growth is one of the most critical challenges for the development of Li metal batteries. Here, we report for the first time the growth of dendrite-free lithium films with a self-aligned and highly compacted nanorod structure when the film was deposited in the electrolyte consisting of 1.0 M LiPF6 in propylene carbonate with 0.05 M CsPF6 as an additive. Evolution of both the surface and the cross-sectional morphologies of the Li films during repeated Li deposition/stripping processes were systematically investigated. It is found that the formation of the compact Li nanorod structure is preceded by a solid electrolyte interphase (SEI) layer formed on the surface of the substrate. Electrochemical analysis indicates that an initial reduction process occurred at ∼ 2.05 V vs Li/Li(+) before Li deposition is responsible for the formation of the initial SEI, while the X-ray photoelectron spectroscopy indicates that the presence of CsPF6 additive can largely enhance the formation of LiF in this initial SEI. Hence, the smooth Li deposition in Cs(+)-containing electrolyte is the result of a synergistic effect of Cs(+) additive and preformed SEI layer. A fundamental understanding on the composition, internal structure, and evolution of Li metal films may lead to new approaches to stabilize the long-term cycling stability of Li metal and other metal anodes for energy storage applications.

Single-crystal FeFe(CN)6 nanoparticles: a high capacity and high rate cathode for Na-ion batteries

Prussian blue analogues are actively explored as low cost and high capacity cathodes for Na ion batteries; however, their applications are hindered by low capacity utilization and poor cyclability of these compounds. Here we show that this problem can be solved by controlling the purity and crystallinity of the Prussian blue lattices. As a model compound, single-crystal FeIIIFeIII(CN)6 nanoparticles are synthesized and found to have a sufficiently high capacity of 120 mA h g−1, an exceptional rate capability at 20 C and superior cyclability with 87% capacity retention over 500 cycles, showing great promise for Na ion battery applications. More significantly, these results provide a new insight into the intercalation chemistry of Prussian blue analogues and open new perspectives to develop Na storage cathodes for widespread applications of electric energy storage.

Improved electrochemical performances of nanocrystalline Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode material for Li-ion batteries

Layered Li[Li0.2Co0.13Ni0.13Mn0.54]O2 nanoparticles were synthesized by a simple polymer-pyrolysis method and then coated with 3 wt% Al2O3 to form a ∼4 nm thick protective skin. The Al2O3-coated Li[Li0.2Co0.13Ni0.13Mn0.54]O2 electrode demonstrates a high initial coulombic efficiency of 96.1%, a large reversible capacity of ∼311 mAh g−1, and a good cyclability with 83.8% capacity retention after 70 cycles. Particularly, this material can deliver a quite high capacity of ∼239 mAh g−1 at a high rate of 400 mA g−1. This superior electrochemical performance results from the well-crystallized nanocores and effective surface modification of the material. The former provides a short diffusion path and fast transport channels for lithium ion insertion/extraction reactions and the latter restrains the elimination of oxide ion vacancies and metal ion rearrangement during charge–discharge cycling. Due to their simplicity and applicability, the synthetic method along with the surface modification technique is easily adopted to make high performance xLi2MnO3·(1 − x)LiMO2 materials for practical battery applications.

A low cost, all-organic Na-ion Battery Based on Polymeric Cathode and Anode

Current battery systems have severe cost and resource restrictions, difficultly to meet the large scale electric storage applications. Herein, we report an all-organic Na-ion battery using p-dopable polytriphenylamine as cathode and n-type redox-active poly(anthraquinonyl sulphide) as anode, excluding the use of transition-metals as in conventional electrochemical batteries. Such a Na-ion battery can work well with a voltage output of 1.8 V and realize a considerable specific energy of 92 Wh kg−1. Due to the structural flexibility and stability of the redox-active polymers, this battery has a superior rate capability with 60% capacity released at a very high rate of 16 C (3200 mA g−1) and also exhibit an excellent cycling stability with 85% capacity retention after 500 cycles at 8 C rate. Most significantly, this type of all-organic batteries could be made from renewable and earth-abundant materials, thus offering a new possibility for widespread energy storage applications.